1. Field of the Disclosure
Embodiments disclosed herein generally relate to a method and apparatus used for stabilizing a mobile offshore unit. More specifically, embodiments disclosed herein relate to an improved stabilizing chamber that is used with mobile offshore units, such as submersible rigs, semi-submersible rigs, and jackup rigs.
2. Background Art
As the search to find energy resources continues, the increased demands in energy and decreased amounts of energy resources have required the exploration and production of the energy resources to be moved into more remote locations. For example, to find substantial reservoirs having energy resources, exploration has moved into remote geological offshore locations, such as bays, oceans, and seas. As drilling operators and engineers are well aware, these offshore locations present many problems that are not common with drilling on land.
To facilitate the exploration and production of energy reservoirs within the offshore locations, many different types of mobile offshore units have been developed. These mobile offshore units are generally self-contained floatable or floating drilling machines, in which the units may be transported to the offshore locations for production of energy sources. Examples of mobile offshore units include submersible production and/or drilling rigs, semi-submersible production and/or drilling rigs, and jackup rigs, amongst other various production and drilling rigs.
A submersible rig usually includes a floating vessel having a platform that is primarily supported on large float-like or pontoon-like structures. These structures are submerged below the sea surface, and once the submersible drilling rig is at the desired location, the submersible drilling rig is flooded with water until resting on the seafloor. Similarly, a semi-submersible rig also includes a floating vessel having a platform primarily support by large float-like or pontoon-like structures. However, a semi-submersible rig, when flooded with water, does not rest on the seafloor. Instead, the semi-submersible rig is anchored to the seafloor with long cables or chains. Because a semi-submersible rig does not need to be resting on the seafloor, the semi-submersible rig may be used in deeper offshore locations, as compared to the submersible rig.
The mobile offshore units, however, may be difficult to manage and control when in the offshore environment. For example, including the horizontal loads that are distributed upon a mobile offshore unit, the mobile offshore unit must also be able to withstand the forces from the waves, wind, and current. This delicate balance of all of these forces requires precision and increased stability for the mobile offshore unit.
Further, when the mobile offshore units are being flooded with water to submerge, the mobile offshore units have even more factors to consider. For example, as water is being received within the mobile offshore units, the center of gravity and the center of buoyancy of the mobile offshore unit are both rapidly changing. Furthermore, the operator must make sure that the different portions of the mobile offshore unit are being flooded at proportional rates. Otherwise, if one portion of the mobile offshore unit happens to flood more quickly and retain more water than another portion of the mobile offshore unit, this may cause the mobile offshore unit to tilt, and possibly even capsize.
Furthermore still, when the mobile offshore units are being transported to a desired offshore location for production of energy sources, the mobile offshore units need to maintain a relative velocity while withstanding the forces of the environment. This relative velocity requirement of the mobile offshore units further increases the degree of precision and stability that these mobile offshore units must have. Accordingly, there exists a need to increase the stability of a mobile offshore unit, particularly as the mobile offshore unit is in the process of submersion and/or transportation.